Non-electronic forms of clandestine communication can be found in ninjutsu texts such as the Gunpo Jiyoshu, Bansenshukai, and scrolls of Chikamatsu Shigenori. Creating your own methods of encrypting messages is easy enough when you understand the basics of communication and non-electronic signalling principles. In the vid. below, I give a short demonstration of how the shinobi method Goshiki-Mai (five color rice) can be used.
Goshiki-Mai (5 Colored Rice): This ancient communication method of ninjutsu entails the deposition of colored rice within an area of operations to secretly convey information to allies. The shinobi would use blue, red, yellow, black, and purple dyes to color the rice which would be carried on his/her person in bamboo tubes. The rice would be placed in accord with a pre-established, closely guarded crypt-key to avoid unwanted decryption of the message. Different arrangements of the colored rice conveyed distinct meanings intelligible to only those possessing the crypt-key.
Method Disadvantages: 1. potential for disturbance of the coded message by animal, climactic, or human interaction 2. short communication distance and lack of reception precision (recipient must be in close proximity -20 ft. minimum- of the rice in order to decode the message) 3. potential to arouse suspicion (Why is there colored rice on the ground?)
Method Advantages: 1. ease of use (message can be encoded quickly if the crypt-key is memorized) 2. communication medium doubles as a food source 3. message can be destroyed quickly 4. message may appear as random noise to interceptors
Suitable Use: This method is suitable when the weather is not expected to produce high winds or precipitation (rain, snow, etc.). Leave messages in inconspicuous, but readily visible places. You may inform your communications team on what specific placement method is preferred (i.e. by trees, on rocks, along roads, etc.). The total amount of colored rice to carry should not be cumbersome, and the amount dispensed for each coded message should be kept to a minimum. Be sure to devise a crypt-key, patterns for rice placement, and instruct each communications team member on the type of information that is to be conveyed (this will vary by the scenario). Do not allow for witnesses of message placement and inform team members on protocol if a coded message seems to be tampered with (i.e. advise senders to practice message redundancy, placing the same code twice in two different but proximal areas). Above all, guard the crypt-key.
Communications Essentials One Should Bear in Mind
Message: What is to be communicated?
Sender: From whom is the message sent?
Receiver: To whom is the message addressed?
Medium: Is the transmission electronic (radios, cell-phones, internet, etc.), static (physical objects or arranged in accord with a specific code), biological, or a combination of the three? If biological, is the medium gestural or verbal?
Signal Security: What is the transmission code or crypt-key? How is the message made intelligible? What language is used?